1. Field of the Invention
The present invention relates to a negative pressure supply apparatus for automobiles, and more particularly, to a negative pressure supply apparatus for automobiles having a vacuum tank which stores a negative pressure therein and a vacuum pump which generates compulsorily the negative pressure to the vacuum tank.
2. Description of Prior Art
A negative pressure supply apparatus for autombiles stores a negative pressure generated from an engine intake manifold for automobiles in a vacuum tank, and supplies the negative pressure to a control apparatus for a driving force source as occasion demands.
The negative pressure supply apparatus for automobiles includes a vacuum tank which generates compulsorily the negative pressure in the vacuum tank when the negative pressure in the vacuum tank goes over a predetermined setting pressure value and becomes toward an atmospheric pressure.
The negative pressure supply apparatus for automobiles supplies a negative pressure of above a predetermined setting pressure value to the control apparatus. The negative pressure supply apparatus stores an engine negative pressure in the vacuum tank via a check valve and consumes the negative pressure in the vacuum tank by operation of the control apparatus. When the engine negative pressure becomes low, for example turbo operating time, accelaration stepping time etc, the negative pressure in the vacuum tank becomes low and the control apparatus beings to operate abnormally.
To prevent the above inconveniences, the negative pressure in the vacuum tank is detected by a vacuum switch, and a motor rotates to operate a vacuum pump. Then the vacuum pump discharges air in the vacuum tank outside and the negative pressure value in the vacuum tank as raised above the predetermined setting pressure value. The check valve compares the engine negative pressure with the negative pressure in the vacuum tank and, when the engine negative pressure is higher than the negative pressure in the vacuum tank, the air in the vacuum tank flows into the engine.
In, for example, Japanese Utility Model Publication No. 9115/1984, a negative pressure supply apparatus for automobiles is proposed which is designed to integrate a vacuum tank with a vacuum pump. In the negative pressure supply apparatus proposed in the above Japanese Utility Model Publication, the vacuum tank is side by side with the vacuum pump. A motor for driving the vacuum pump is disposed on an intermediate space formed between the ouside of the vacuum pump and the outside of the vacuum tank. The vacuum pump is united with the vacuum tank, so that the piping structure for connecting between the vacuum pump and the vacuum tank is abolished and the negative supply apparatus structure is simplified.
However, the establishment spaces of the vacuum pump and the vacuum tank exist separately and distinctly, and further the motor for driving the vacuum pump is disposed outside of the vacuum pump. Accordingly, in the conventional negative pressure supply apparatus for automobiles, the establishment spaces of the negative pressure supply apparatus become large and the establishment place is not allowed to be freely in the negative pressure supply apparatus.